Having already seen Leroy Sane sustain an ankle injury that forced the Germany winger out of the game in the first half, Guardiola then turned to the Main Stand of the Cardiff City Stadium and shook his head in bewilderment as the home supporters applauded Joe Bennett off the pitch after the defender had been shown a red card for a stoppage-time foul on Brahim Diaz.

Bennett was the man who scythed down Sane shortly before half-time -- a tackle that earned a booking and prompted the German national team's official Twitter feed to call for Cardiff's players not to injure their international stars -- and the still footage of the challenge are the kind that should be accompanied by an X-rating.

All top teams must overcome physical intimidation at times to beat a more limited opponent, but Cardiff's approach in this game was a throwback to the bad old days when football was like the Wild West. Their approach seemed to be "if you can't beat them, kick them," and Sane and Diaz weren't the only players on the receiving end of some shocking challenges. Ilkay Gundogan, Fernandinho and Sergio Aguero were also targeted by opposing defenders; Guardiola marched onto the pitch at the end of the game to complain forcefully to referee Lee Mason about his failure to properly deal with the home team's rough-house tactics.

Pep Guardiola was furious at Cardiff's aggressive play, as well as the referee's unwillingness to intervene.

"You have to protect the players," said Guardiola. "I do not understand the goal [being disallowed], but that I can accept. But the referees have to protect the players --and not just my players, all players. Where there is fault, there is fault, and when it is dangerous, it is dangerous. You are not more brave for kicking.

"Sane will be out, I am not sure how long for, I am not a doctor."

Warnock's response offered little sympathy or contrition at the same time as it justified Guardiola's complaints.

"We're in England," said Warnock. "You are going to get challenges like that."

Forgiving Warnock's geographic faux-pas for a moment (Cardiff is the capital city of Wales and isn't in England), the suggestion that challenges such as Bennett's on Sane are a regular occurrence in English football is the kind that makes the likes of Guardiola roll his eyes in exasperation. They're not the norm, not anymore, and they are being stamped out, but City have found themselves facing up to opponents who have tried to knock them off their stride with foul play.

Manchester United and Tottenham both tried and failed to physically intimidate City in the Premier League in December, but Crystal Palace "got stuck in" during the 0-0 draw at Selhurst Park on New Year's Eve and ended the game with Jason Puncheon suffering a cruciate ligament injury following a wild challenge on Kevin De Bruyne.

De Bruyne looked to be seriously injured at the time, but the Belgium international somehow recovered in time to play against Watford two days later. Yet the nature of Puncheon's challenge suggested that teams are running out of legitimate ways to stop City. Cardiff took it to another level, but De Bruyne claimed after the game that City were expecting what came.

"We knew how they played," he said. "They caught us a few times, and that is football, but obviously Leroy Sane is injured now and, hopefully that is not too bad."

Sane's injury could be significant to Man City's hopes for winning all competitions this season.

Cardiff's approach was short-sighted and basic in the extreme, though, especially when compared with Bristol City's attempts to beat Guardiola's men during their two-legged Carabao Cup semifinal earlier this month. In both games, Bristol City opted for attacking football rather than foul play. Lee Johnson's side pushed City close by taking them on at football, but Cardiff lacked the courage to do that.

Guardiola is right to be alarmed by the lack of protection afforded to his players by the officials on this occasion, but having so comprehensively beaten Cardiff, perhaps future opponents will stop short of attempting to kick City off the pitch. But that may be wishful thinking and Paul Dickov, the former Man City forward, summed up the growing concern at the lack of protection with a tweet after the game.

Dickov tweeted, "Great professional performance by @ManCity great to see the skipper back @VincentKompany. Officials appalling again, could have been 3 serious injuries not for the first time, something has to be done about this, before someone suffers a serious injury."

That moment may have arrived with Sane's injury on Sunday.

Mark Ogden is a senior football writer for ESPN FC. Follow him @MarkOgden_